A vacuum is drawn over a beaker of sliced cucumber covered in a clear dressing. The cucumber outgases, making bubbles. When the atmosphere is readmitted, the dressing is forced into the cucumber, rendering it translucent and seasoned.
A polycarbonate bell jar with a volume of about three liters is centered on the base, with attention to the seal. The vacuum pump tube ID is the same as the outlet tube OD, so attach by hand. Vacuum release by sliding the vinyl tube off of the outlet.
The vacuum pump is the oil-less variety, and is not bothered by water. The pump is...
Dark red iron[III] solution is rapidly reduced to colorless iron[II] by addition of tin[II] chloride solution, with the rate depending on concentration and temperature.
Four medium footed cylinders are prepared with 100 ml of ferric chloride solution 0.01M with potassium thiocyanate solution added to make the dark red complex. One of the solutions should be hot, so just the iron and thiocyanate solutions in that cylinder, with a 150ml beaker for the demonstrator to fill with hot water from the water cooler, right before the demonstration.
A magnesium ribbon is held with tongs and lit with a match or torch, making a bright flame that consumes the ribbon from the bottom up.
The ribbon should be about 20-30 cm long. Hold the ribbon with the tongs high and at arms length. Let the magnesium ribbon hang at a steep angle but not vertical. Light the bottom of the ribbon by bringing the end of the torch flame up to ribbon. Magnesium will melt before it lights, so carefully with the torch. The ribbon can also be lit with a wooden match.
Wear safety glasses and don't look directly at the flame.
Hydrogen peroxide 30% in a large round flask decomposes to boiling water and oxygen when postassium iodide is added.
The 12L Round Bottom Flask is set on white C-Fold towels covering a large cork ring on the lab bench. 100-150 ml of 30% hydrogen peroxide is carefully poured in. The liquid should be visible against the white towels from the perspective of the class, and any camera, if used.
The catalyst is 5 g of potassium iodide in a small plastic weighing boat labeled KI.
Safety goggles and gloves. Raise the projection screen and make sure the flask is...
Vinegar and two different amounts of baking soda in plastic soda bottles with balloons.
Two 500ml PETN soda bottles of the same make, split a bottle of vinegar between them.
11" balloons are pre-inflated with dry air, with care taken not to stretch the neck of the balloon. Into the balloons with a funnel go one, two teaspoons of baking soday. With 250 ml of vinegar, that's like six liters of gas potential if one carbon dioxide comes from one acid hydrogen ion.
Tap the baking soda powder down away from the neck of the balloon. Stretch the neck and place it over the top...
A light bulb is lit when the conductivity probe is immersed in an ionic solution.
The solutions are all in labeled 250ml beakers. All are about 150 ml of 0.1M sol'n. In order, the solutions are: tap water, distilled water, sodium chloride, sucrose, acetic acid, hydrochloric acid, sodium hydroxide, ethanol, and barium sulfate. (See video: http://youtu.be/4WillWjxRWw?hd=1)
The simple conductivity tester is on the bench, for the instructor to plug in. An 800ml beaker with 400 ml of distilled water is provided as...
Several samples are weighed on the balance; each is a mole.
The electronic scales are set up in front of the video camera. In a secondary container on the scale platform is a cube of lead weighing 208 g., 18 g of water in a bottle with an empty bottle for tare, and 200.6 g of mercury in a bottle with an empty bottle for tare.
Sodium chloride solution is added to silver nitrate solution and a white precipitate of silver chloride is instantly formed.
The silver nitrate solution is around 0.1M, and the sodium chloride solution around 0.5M. Pour the sodium chloride sol'n into the silver nitrate to avoid leaving traces of silver nitrate in the empty beaker.
Wear safety glasses and gloves to prepare and perform this demonstration.
OHP representation of lines of force using bar magnet and iron filings.
What it shows:
The magnetic field lines of the Earth can be represented by the field lines of a bar magnet.
How it works:
The Earth's magnetic field is basically a magnetic dipole. It can therefore be represented to first approximation by the field of a bar magnet. The shape of the field lines can be highlighted by the sprinkling of iron filings, or by the use of plotting compasses. The latter method has the advantage of showing the variation of dip...
The aberration of starlight is the shift in the position of the image of a star due to the rotation of the Earth about the Sun, and is a consequence of the finite velocity of light. For a star directly overhead, a telescope will have to be angled by v/c to the vertical where v = velocity of the Earth in space, in order that the telescope be pointing at the star. The equipment necessary to show aberration is one umbrella.